1. Field
The present invention relates to a method of constructing a vertical concrete column member, such as the pylon of a bridge and a bridge pier, using a slip form and an apparatus for measuring the strength of concrete for the method and, more particularly, to an apparatus for measuring the strength of concrete using a surface wave velocity including an ultrasonic transmission and reception probe configured to include an surface wave velocity measurement device including an ultrasonic transmission probe and an ultrasonic reception probe and to measure the propagation velocity of an surface wave propagating along concrete and measure the strength of the concrete based on the measured propagation velocity and a method of constructing the slip form of a concrete column member capable of reducing the construction period by raising a concrete form rapidly and safely in such a way as to determine the slip-up time of the slip form based on the strength of concrete measured by the apparatus for measuring the strength of concrete in performing a slip form construction method of producing a vertical concrete column member, such as the pylon of a bridge or a bridge pier, by casting concrete while stepwise raising a concrete form (i.e., a slip form) that is slid.
2. Description of the Related Art
When constructing a bridge, in particular, a concrete column member, such as the concrete pylon or concrete pier of a long bridge, the concrete is stepwise casted. That is, a concrete column member having a desired height is constructed in such a way as to cast concrete to a predetermined height, cure the cast concrete so that it has predetermined strength, and cast the concrete over the cured concrete again.
In this construction, a concrete form that slides and moves, that is, a slip form, is mainly used. In a construction method using the slip form, a concrete column member having a desired height is constructed by repeating a process of assembling the slip form, installing reinforcing bars inside of the slip form, casting concrete, curing the concrete, installing reinforcing bars on the cured concrete, raising the slip form, and placing concrete. Next, the slip form is dismantled.
In the slip form construction method of constructing a concrete column member using a slip form as described above, the setting time of concrete is very important. The term “early setting time” herein means a curing time, that is, the initial condensation reaction time of concrete that the concrete is taken to have strength that may maintain structural stability even though the concrete exists from the slip form after the concrete is cast. The early setting time is a very important factor that determines the time that the slip form is raised, that is, a “slip-up time of slip form”. The entire construction period and construction efficiency depend on the slip-up time of the slip form. Accordingly, in constructing a column member using a slip form, the casting velocity of concrete and the slip-up time of the slip form can be determined only when the concrete setting time is accurately known.
The inventors of the present invention studied that the strength of concrete could be measured using the propagation velocity of an surface wave that propagates along concrete, released a thesis entitled “A Study on the Determination of the Slip-up Speed for Slip-Form System using Ultrasonic” in the 36th Regular Academic Conference of Korean Society of Civil Engineers that was held in 2010 as disclosed in Prior Technical Document, and also published a thesis entitled “A Study on the Determination of the Slip-up Speed for Slip-Form System Using the Speed of a surface Wave in Concrete” in the 2010 Spring Academic Conference sponsored by Journal of the Korea Concrete Institute (JKCI) that was held in November 2010.
Thereafter, the inventors of the present invention have developed an apparatus for measuring the velocity of an surface wave which has a new construction and has a construction easily installed in a slip form, in order to commercialize technology for measuring the strength of concrete using the propagation velocity of an surface wave that propagate along concrete, additionally induced a new and advanced method of constructing a slip form for a concrete column member which constructs the concrete column member by raising the slip form based on the strength of concrete measured by the apparatus for measuring the strength of an surface wave, and filed a Korean Patent Application No. 10-2010-0121211 in 2010.